Irradiation chamber



Dec. 16, 1969 A. KUENZLI 3,484,612

IRRADIATION CHAMBER Filed Aug. 24, 1965 2 Sheets-Sheet 1 Inventor: ALBERT KUENZLI AT-ro EYS Dec. 16, 1969 A. KUENZLI 3,484,612

IRRADIATION CHAMBER Filed Aug. 24, 1965 2 Sheets-Sheet 2 Fig. 3

1- Invcnf0r: ALBERT KUENZLI United States Patent US. Cl. 250106 6 Claims ABSTRACT OF THE DISCLOSURE The radiation chamber has the radiation sources mounted in the ceiling so as to be retractably moved into and out of the chamber from above. The radiation sources are slidably mounted in a helical tube inclined to the horizontal at an angle slightly less than the angle of friction of the radioactive source.

The invention relates to an irradiation chamber with a source of radiation retractable into a sheilding block, characterized in that the shielding block forms part of the roof of the chamber.

In known irradiation chambers with sources retractable into a shielding block, the source is moved out of the block sideways or raised into the working position from the bottom. In these irradiation chambers it is rather difiicult to irradiate large objects evenly. The arrangement of the shielding block in the floor of the irradiation chamber also has the disadvantage that the fioor has to be kept very clean so that impurities do not enter the shielding block with the source and perhaps affect operation of the conveying mechanism.

The object of the invention is to make an irradiation chamber which also allows large objects to be irradiated and has a level, easily cleaned floor, in which the mechanism for the source cannot be damaged even if fluid material being irradiated leaks.

The invention will now be described with reference to an embodiment shown diagrammatically in the accompanying drawings. In these:

FIG. 1 shows a section through the irradiation chamber according to the invention, partly shortened in the vertical direction;

FIG. 2 shows another embodiment of the guide tube for the source of radiation;

FIG. 3 shows another embodiment of the conveying and storing means for the. cable for the source of radiation, and

FIG. 4 shows a different embodiment of the parts of the source of radiation, on a larger scale than in FIG. 3.

In FIG. 1 an irradiation chamber 1 has a floor 2 and a roof 3 carrying a shielding block 4. Two tubes 5 are cast integrally with the shielding block; a chain of radiation sources 6 moves in each tube. The tubes are helical in part, the pitch of the helix being slightly less than the angle of frictiOn of the source The sources comprise radioactive materials 7, e.g. cobalt 60, in cylindrical capsules joined by articulations 8. Each chain of sources 6 is joined to a cable 9 running in a tube 10. These tubes 10 are smaller in diameter than the tubes 5 and lead to a drum 11, to which the cable ends are attached and which has grooves for receiving the cable. The ends of the tubes 10 are joined at ball and socket joints 12 to pivoting tubes 13 which guide the cable between the tubes 10 and the grooves in the drum. The drum 11 is tightly enclosed by a housing 14 and can be operated by a handwheel 17 by way of a transmission consisting of cogs 15, 16.

3,484,612 Patented Dec. 16, 1969 At the bottom of the shielding block 4, tubes 20 are joined to the tubes 5 in bearings 18 allowing rotation. The lower portions of the tubes 20 are vertical and the upper portionsthose adjacent to the bearings 18--are bent in an S-shape. By means of this construction the vertical portions of the tubes are at a distance, viz an eccentricity E, from the vertical axes of the bearings 18. In the arrangement shown in FIG. 1 the bottom ends of the tubes 20 are. supported on arms 21 rotatable about pins 22. The tubes 20 can therefore be pivoted about an axis leading through the bearings 18 and the pins 22. The eccentricity E is equal to or only slightly less than the distance of the bearings 18 from the center of the arrangement. This allows the vertical portions of the tubes 20 to be swung in as far as the. middle of the arrangement. Between the tubes 20 there is room for the material 23 undergoing irradiation.

To prepare for irradiation, the material 23 is set up in the space between the tubes 20, the sources being retracted into the tubes 5 and the tubes 20 being moved apart. The tubes 20 are. then swung in until they are at the desired distance from the material. The irradiation chamber is left and the sources 6 are lowered from the tubes 5 into the tubes 20 by operating the handwheel 17, so that irradiation begins. After the desired radiation dose has been administered, the drum 11 is moved, the sources 6 are retracted into the tubes 5, and, once the tubes 20 have been moved apart, the irradiated material can be removed from the chamber.

This irradiation chamber has the advantage that the material for irradiation is set up on a practically level floor, which, moreover is easily cleaned if contaminated, e.g. by the said material. There is practically no limit to the height of the chamber and the height of the material 23, since the sources are freely suspended in the tubes 20 and these tubes 20 can be made relatively long and with correspondingly long chains of sources.

The helical path of the tubes 5 prevents radiation from getting out through the openings of the tubes when the sources are retracted. Inclination of the tubes is an advantage insofar as it prevents friction or resistance of these sources when leaving the shielding block; however, this inclination is preferably made less than the angle of friction of the sources, since it must not be possible for a source to slide out in the event of damage to the cable.

If the pivoting arms 21 obstruct the floor, the construction shown in FIG. 2 can be chosen. Here a tube 30 is attached only at its upper end, by which it is pivotable in a bearing 31. In this case, the tube 5 may, for example, be provided with a threaded flange 32 for screwing on a retaining nut 33 enclosing a flange 34 on the tube 30. In this embodiment the tube can be removed by unscrewing the nut 33 so that it does not prevent manipulation when material is being set up for irradiation. This is particularly useful where there is a larger number of tubes than the two shown in FIG. 1. Larger radiation doses may be obtained by arranging a larger number of tubes in a circle round the material.

FIG. 3 shows an embodiment of the cable drum in which, for example, when the cable is rolled up, the level at which it enters the groove in the drum remains constant, so that the pivoting tube 13 shown in FIG. 1 becomes superfluous. In this embodiment a drum is mounted on a shaft 41 by means of a thread 42, and the pitch of this thread is equal to the pitch of the grooves in the drum 40. A cog 43, which may, for example, engage the cog 16 shown in FIG. 1, is movable on the shaft 41. On rotation of the drum 40, the thread 42, guided in a fixed nut 44, causes the height of the drum 40 to change so that the point 45 at which the cable leaves the drum is always at the same level. The tubes 10 can therefore communicate with the drum directly at this point, and there is no need of a pivoting insert tube.

FIG. 4 shows a further embodiment of the chain of individual sources of radiation. Radioactive parts 50 are enclosed in cylindrical capsules 51 with a ball 52 at one end and a cup 53 at the other. The ball and cup of adjacent capsules form a ball and socket joint. The capsules have annular projections 54 to guide them in the tubes 5, 20, 30. The joints connecting the individual links in a chain of sources, as shown in FIGS. 1 and 4, allow the tubes to be made with a number of bends. The annular projection 54, which is as near as possible to the ball and socket joint, discourages the chain from jamming in the tubes.

The cable drums described, on which the cable is wound, may be replaced by a drum serving only to drive the cable. In this case coupling of the cable to the surface of the drum causes the cable to move; in the drawnout state, with the source retracted, the cable may be stored, for example, in a tube outside the shielding block. The drum can be coupled to the cable either by friction, e.g. by means of a pinch roller, or by means of a toothedtype engagement. A Teleflex cable may, for example, be used; this has a helical outer winding of steel wire which can act as a sort of toothed rack. In this case matching cuts like a helical toothing are made in the surface of the drum. Here, as in the two embodiments described, the drum may be located outside the shielding block.

The arrangement according to the invention may, of course, comprise known regulating means for remote control. For example, when the drum is driven by an electric motor, limit switches may be used to switch it olf in one or other limit position of the source. Moreover, warning and locking devices may be used to prevent people entering the irradiation chamber when the sources are down.

What is claimed is:

1. An irradiation chamber comprising a roof having a shielding block carried therein;

a floor spaced from said roof to define a space therebetween for mounting of a material to be irradiated therein;

a plurality of passageways in said shielding block, each said passageway slidably receiving a source of radiation therein;

a plurality of substantially S-shaped guide tubes disposed symmetrically about a centerline between said root and floor, each said guide tube being rotatably secured to a lower end of one of said passageways for guiding a source of radiation therein through the space between said roof and fioor whereby said sources of radiation can be variably positioned with respect to a material position therebetween within the space between said roof and floor; and

means for moving said sources of radiation into and out of said guide tubes.

2. An irradiation chamber as set forth in claim 1 further comprising at least one curved passageway in said shielding block slidably receiving said source of radiation therein.

3. An irradiation chamber as set forth in claim 1 which further comprises at least one helical tube integrally mounted in said shielding block, said helical tube slidably mounting said source of radiation therein whereby the helical path of said tube prevents radiation from escaping through said tube when said source of radiation is retracted therein.

4. An irradiation chamber as set forth in claim 3 wherein the inclination of said helical tube to the horizontal is slightly less than the angle of friction of said source of radiation.

5. An irradiation chamber as set forth in claim 1 further comprising a conveying device in said roof and a flexible cable connected to said conveying device and said source of radiation whereby said conveying device is adapted to move said source of radiation into and out of the space between said roof and floor.

6. An irradiation chamber as set forth in claim 1 further comprising a plurality of cylindrical capsules housing said source of radiation, each said capsule being joined to an adjacent capsule in an articulated manner.

References Cited UNITED STATES PATENTS 3,088,032 4/1963 Brunton 250-106 3,120,613 2/1964 Prest 250-106 3,121,168 2/1964 Bangs et a1. 250-406 3,147,383 9/1964 Prest 250106 RALPH G. NILSON, Primary Examiner A. B. CROFT, Assistant Examiner U.S. C1. X.R. 2SO-108 

